The present invention relates generally to an apparatus and a method for moving fluids, and more particularly to a fan blade and a method of moving fluids with a fan blade.
A typical fan assembly consists of a hub, a multi-wing spider, and two or more blades, although in some assemblies the hub and spider can be an integral unit, or the spider and blades can be an integral unit. In some cases, it is even possible to employ a fan assembly in which the hub, multi-wing spider, and blades are a single integral unit. In those fan assemblies in which fan blades are attached to a spider wing, each spider wing is often attached with a blade through riveting, spot welding, screws, bolts and nuts, other conventional fasteners, and the like.
Fan assemblies are employed in a large number of applications and in a variety of industries. However, there exist a number of common design criteria for fans in many of such applications: fan efficiency, noise, and the like. For example, it is desirable for a fan assembly of a residential or commercial air conditioning system to be as efficient and quiet as possible, resulting in energy savings and a better operating system.
With continued reference to air conditioning system applications by way of example only, the fans in such systems are typically directly driven by a motor to draw airflow through condenser coils to achieve a cooling effect. Existing condenser fan assemblies employ rectangular blade shapes. Although these fans will generate sufficient airflow to meet varied cooling needs when the fan blades are pitched properly, such fans also radiate high levels of noise during operation and can be relatively inefficient.
In many applications, the upstream airflow of a rotating fan is partially blocked by a motor or other driving unit, frame or other structural members, and other elements. For example, in a typical condenser cooling application, the upstream airflow of a rotating fan is often partially distorted due to the blockage of a compressor, controlling panels, etc. As a result, tonal and broadband noise is often generated by the leading edges of the rotating fan blades as they cut through the flow distortion (i.e. turbulence). In addition, each segment of the fan blade leading edge along the radial direction can act as a noise radiator.
In light of the above shortcomings of conventional fans, there are increasing market demands for fans that can generate sufficient air for cooling at reduced noise levels. In addition, fan assemblies and fan blades that are durable, easy to manufacture, easy to assemble, and are inexpensive are highly desirable for obvious reasons.
The present invention employs improved fan blade shapes to generate improved fan blade performance in one or more manners (i.e., increased fan efficiency, lower fan noise, greater fluid moving capability, and the like). In some embodiments, the fan blade is shaped to reduce noise during operation thereof.
The fan blade of the present invention can be formed from a flat blank bent to a desired shape to form the fan blade. Alternatively, the fan blade can be cast, molded, or produced in any other manner desired.
In some embodiments of the present invention, the fan blade has a front side, a rear side, an inner attachment portion, an outer edge, a curved leading edge and a curved trailing edge. The outer edge can define an arc between a forward position and a rearward position of the fan blade. In some embodiments, the leading edge extends outward and intercepts the arc of the outer edge at the forward position, and the trailing edge extends outward to the rearward position.
The shapes of the blades of the various embodiments of the present invention can be defined at least in part by one or more angles or lengths, including the radius of the fan assembly at different locations on the blade (e.g., the radius of the fan assembly RL at a leading edge of the fan blade and/or the radius of the fan assembly RT at a trailing edge thereof), a radius of a circle that coincides or substantially coincides with a majority or all of the length of a trailing edge of the blade, an angle at which a leading edge of the fan blade is swept forward, an angle at which a trailing edge of the fan blade is swept forward, the chamber-to-chord ratio of the leading edge of the fan blade, the chamber-to-chord ratio of the trailing edge of the fan blade, the chamber-to-chord ratio of a cross-section of the blade at various radial distances of the blade (from the rotational axis thereof), and an angle of the outer radial portion of the blade with respect to a plane passing perpendicularly through the rotational axis of the blade. Blades falling within the spirit and scope of the present invention can be at least partially defined by the size of any one or more of these blade parameters.
In some embodiments, the angle at which the leading edge of the fan blade is swept forward is formed by a straight line having a length equal to RL extending from a given axis coinciding with the axis of the fan to the forward position of the fan blade (mentioned above) and a line extending from the axis to a first position on the leading edge and having a length equal to about 0.5 RL wherein the angle xe2x88x9dL is equal to at least 35 degrees. In other embodiments, this angle is formed by a straight line extending from the axis to the forward position of the fan blade and a line extending from the axis to a first position on the leading edge and having a length equal to about 0.65 R, wherein R is the radius of the fan assembly and xe2x88x9dl, is between 15 and 45 degrees, 20 to 35 degrees, or 25 to 30 degrees (in different embodiments of the present invention).
In another aspect, the chamber-to-chord ratio of the leading edge of the fan blade in some embodiments is larger than about 0.10 but less than about 0.20, wherein LL is the length of a straight line from the first position to the forward position and HL is the maximum distance from LL to the leading edge as measured from a straight line perpendicular to LL and extending to the leading edge. In other embodiments, the chamber-to-chord ratio of the leading edge of the fan blade is between 0 and 0.22, 0.05 and 0.17, or 0.08 and 0.13 (in different embodiments of the present invention).
In a further aspect, the angle at which a trailing edge of the fan blade is swept forward is formed by a straight line having a length equal to RT extending from the axis of rotation of the fan assembly to the rearward position (mentioned above) and a line extending from the axis to a second position on the trailing edge of the blade and having a length equal to about 0.5 RT, wherein xe2x88x9dT is at least 30 degrees but less than 40 degrees. In other embodiments, this angle is formed by a straight line extending from the axis to the rearward position of the fan blade and a line extending from the axis to a second position on the trailing edge and having a length equal to about 0.65 R, wherein R is the radius of the fan assembly and xe2x88x9dt is between 10 and 35 degrees, 15 to 30 degrees, or 20 to 25 degrees (in different embodiments of the present invention).
In another aspect, the chamber-to-chord ratio of the trailing edge of the fan blade in some embodiments is larger than about 0.10 but less than about 0.20, wherein LT is the length of a straight line from the second position to the rearward position and HT is the maximum distance from LT to the trailing edge as measured from a straight line perpendicular to LT and extending to the trailing edge. In other embodiments, the chamber-to-chord ratio of the trailing edge of the fan blade is between 0 and 0.20, 0.05 and 0.17, or 0.07 and 0.12 (in different embodiments of the present invention).
With regard to the chamber-to-chord ratios of cross-sections of the blade at various radial distances of the blade (from the rotational axis thereof), in some embodiments this camber-to-chord ratio falls between 2.0% and 7.5%, and can be constant or vary with increasing distance from the rotational axis of the fan assembly. With regard to the angle of the outer radial portion of the blade (with respect to a plane passing perpendicularly through the rotational axis of the blade), this angle is between 4 and 15 degrees, 6 and 13 degrees, or 8 and 11 degrees (in different embodiments of the present invention).
Other features and advantages of the invention along with the organization and manner of operation thereof will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings, wherein like elements have like numerals throughout.